"It was very unexpected," Jax said. "When you're 20 years old, you have this Superman entitlement mentality. Like you're indestructible. Thank God I have people in my life that were there to help me deal with this when my reality finally clicked for me. I'm a tough guy, but I don't think I have ever experienced anything scarier."

According to Jax, she felt a lump in her throat while grocery shopping and got herself checked out at an urgent care facility. After undergoing tests, it was revealed that she had 18 tumors on her thyroid, 12 of which were cancerous.

Jax said that she felt "depressed" and was in a "really dark place" in the days leading up to her diagnosis.

In the midst of her recovery, Jax is not letting the setback slow her down. She's planning to participate in the 2016 TCS NYC Marathon on Nov. 6 to help raise funds for Tuesday's Children, an organization dedicated to helping youth and families affected by terrorism.

"Sometimes I think the universe is yelling at me to slow down and I just blatantly ignore it," she wrote in an Instagram post on Monday. "However, my health has to come first. I understand that now."